Operative laparoscopy or pelviscopy is the use of a small rigid endoscope called a laparoscope in association with other instrumentation to view the organs of the abdomen via a 10 or 11 mm cannula or tube inserted through the abdominal wall, usually within the umbilicus. Additional puncture sites are created in the abdomen to pass instrumentation used to manipulate, cut, ligate, suture, staple, suction or irrigate a patient's abdominal contents.
A surgical instrument call a laparoscopic suction-irrigation probe (S/I Probe) is used for four functions: 1. blunt dissection, 2. irrigation of abdominal contents, 3. suctioning of smoke, water and debris from the abdominal cavity, and 4. the introduction of additional instrumentation for cutting or ligature. The S/I probe is a thin walled metal tube with a housing on the proximal end incorporating two trumpet valves and an entry port for additional instrumentation. The valves regulate the flow of irrigation solution and vacuum to the probe tip. The probe is connected to a sterile irrigation line which in turn is connected to an irrigation bottle of sterile normal saline or Ringer's solution. These solutions are either supplied in one liter or 1.5 liter semirigid thermoplastic bottles.
In order to push the solution from the bottle into the irrigation line, pressurized carbon dioxide (CO.sub.2) gas is introduced into the closed bottle from a laparoscopic irrigation bottle pump. Currently, these irrigation bottle pumps are simply mechanical regulators connected to a toggle valve which allows the user to alternate the liquid flow to a second irrigation bottle when the first bottle becomes empty. The irrigation set incorporates two check valves to prevent the flow from the second bottle emptying into the first bottle and allows the user to exchange the empty bottle for a full one.
However, there are problems with these units. The user, who is usually an operating room nurse, must monitor the liquid level in the bottle so that the toggle valve can be switched at the proper time. If the nurse fails to closely monitor the bottle level, the bottle empties and the CO.sub.2 gas will enter the irrigation line. If the line completely fills with gas, the operation is delayed while the irrigation line is purged of gas. This is annoying and time consuming to surgeons and nursing personnel and could be dangerous if too much gas inadvertently enters the abdomen.
A second problem can occur with these irrigation bottle pumps. The source of pressurized gas is usually an "E" size cylinder of CO.sub.2, which is 24 to 29 inches tall, between 17 to 18 lbs. in weight and contains about 1240 liters of gas. Because of the nature of carbon dioxide the maximum cylinder pressure is 830 PSI (gage) at 70.degree. F., which is the pressure at which carbon dioxide changes into a liquid state from a gas (known as vapor pressure). If a pressure gauge is used to monitor the amount of gas in the bottle, the pressure will stay at 830 PSI (gage) until all the liquid CO.sub.2 in the bottle is exhausted. At this point the bottle contains about 208 liters of gas, which is less than 17% of the original filled volume. From this volume to when the cylinder is empty the pressure gauge drops as gas is used. Therefore, most of the time the cylinder pressure gauge does not budge since the vapor pressure maintains a gauge pressure of 830 PSI. If the gauge is not carefully monitored, the pump can run out of gas and delay the operation until a full cylinder is found and reconnected to the pump. Again, this is annoying and time consuming to nursing personnel.
A third problem can often be seen in these mechanical pumps. Because of backlash within the screw mechanism of manually actuated pressure regulators, the selected pressure often drifts from the desired bottle pressure. The user must then readjust the regulator to compensate for this variance. Sometimes the drift can be as much as .+-.5 PSI, thus significantly affecting flow to the S/I Probe. Secondly, if a problem should occur within the pressure regulator and allow excessive pressure to build up within the pneumatic circuit, a dangerous condition would occur without a means to prevent or at least warn the user of this condition.